547. Number of Provinces

Medium

There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city c, then city a is connected indirectly with city c.

A province is a group of directly or indirectly connected cities and no other cities outside of the group.

You are given an n x n matrix isConnected where isConnected[i][j] = 1 if the ith city and the jth city are directly connected, and isConnected[i][j] = 0 otherwise.

Return the total number of provinces.

Example 1:

Input: isConnected = [[1,1,0],[1,1,0],[0,0,1]]
Output: 2

Example 2:

Input: isConnected = [[1,0,0],[0,1,0],[0,0,1]]
Output: 3

Constraints:

• 1 <= n <= 200

• n == isConnected.length

• n == isConnected[i].length

• isConnected[i][j] is 1 or 0.

• isConnected[i][i] == 1

• isConnected[i][j] == isConnected[j][i]

解題

func findCircleNum(isConnected [][]int) int {
    parent := make([]int, len(isConnected))
    for i:=0; i<len(parent); i++ {
        parent[i] = i
    }

    for i:=0; i<len(isConnected); i++ {
        for j:=i + 1; j<len(isConnected[0]); j++ {
            if isConnected[i][j] == 1 {
                union(i, j, parent)
            }
        }
    }
    
    m := make(map[int]bool)
    for _, v := range parent {
        m[findRoot(parent, v)] = true
    }

    return len(m)
}

func union(i, j int, parent []int) {
    fi, fj := findRoot(parent, i), findRoot(parent, j)

    if fi > fj {
        parent[fi] = fj
    } else if fi < fj {
        parent[fj] = fi
    } 
}

func findRoot(parent []int,n int) int {
    if parent[n] == n {
        return n
    }
    return findRoot(parent, parent[n])
}